1. Field of the Invention
The invention relates to a capacitor having a housing which is closed on one end by means of a bottom, which housing accommodates a capacitor wrap provided with electrical connections which are fed out of the housing through the end opposite the bottom, said housing having a crease which is expandable in the axial direction of the wrap and which, when expanded, on its upper side supports the wrap and on its lower side a plug-like member for anchoring one end of one of the electrical connections of the wrap.
A capacitor of this kind is particularly suitable for use as a ballast element in lighting systems using fluorescent lamps. When a capacitor of this kind is overloaded, for example, due to a short-circuit in the system, a substantial development of gas occurs in the capacitor wrap, accompanied by a pressure increase in the capacitor housing. The capacitor will not explode, because due to said pressure increase, the expandable crease is expanded, so that the connection of the capacitor wrap which is anchored in the plug-like member is detached, with the result that the system is switched off and a further pressure increase is prevented.
2. Description of the Prior Art
U.S. Pat. Spec. No. 3,221,225 discloses a capacitor of the described kind in which the wrap is situated between the expandable crease and the bottom of the housing and in which the plug-like member is clamped between the expandable crease and a lid which closes the housing. One of the connections of the capacitor wrap, being passed through the lid and the plug-like member, is tensioned between the plug-like member and the wrap. When a strong overpressure occurs inside the capacitor, this connection is broken.
For assembly of the known capacitor, the following method seems to be necessary. Using a suitable housing, the capacitor wrap is arranged inside the housing, after which the expandable crease is provided; subsequently, the connections of the wrap are passed through the plug-like member and the lid; subsequently, the plug-like member and the lid are arranged on the expandable crease; subsequently, one of the connections is tensioned between the wrap and the plug-like member, and finally the plug-like member and the lid are secured by way of a curled-over edge. This is a rather complex method. Moreover, because the comparatively fragile wrap is very vulnerable, the mechanical operation performed after arrangement of the wrap in the housing must be accurately controlled and carefully executed. An additional tool which is introduced into the housing with a wrap in order to provide a crease in the housing and which is subsequently removed again must also be very carefully and accurately manipulated.